Kia ora and welcome to the December 2017 update from the Transmission Gully team.

Construction update – December 2017

Welcome to December’s construction update for the Transmission Gully project.

The project team wish our neighbours and community a safe and relaxing Christmas and New Year break.

Here’s what’s been happening across the project in the last month, and what’s planned for the holiday season.

Mackays Crossing

In the north, drainage installation for the Coastal Road is nearly complete, as is preparatory earthwork to prepare the ground for the new road. Installation of the ducts for broadband and gas services is progressing and will be largely complete in early January 2018.

Excavation for the bridge that will provide access for Paekakariki residents is complete and we are backfilling the sites with stronger material. As part of this process, we needed to ‘de-water’ the excavation, so ground water from the excavation site was pumped out, and treated in a settlement pond to remove sediment before it was released into the Wainui Stream. Some people may have noticed changes in the water levels and appearance during the pumping. Much of the excavation has now been backfilled, so the “de-watering” is no longer needed and has finished. We work closely with Greater Wellington Regional Council, who monitor our environmental controls across the whole site, to make sure strict water quality standards are met.

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Wainui Saddle area

Bulk earthworks continue at the Wainui Saddle to excavate down to the final road level. Soil nailing, a technique used to stabilise the hillside once earth has been removed, and installing horizontal drains is well underway.

Our construction and environmental teams are busy working on the new permanent channel for the Te Puka Stream. Ecologists and hydrologists play a key role throughout design and construction, ensuring we achieve the desired environmental and stormwater management outcomes.

Specifically-sized boulders called ‘rip rap’ are carefully placed to create the best conditions for a new habitat and to make sure they stay in place during flood events.  There are not enough suitable boulders available in the Wellington region, so we are sourcing some from a quarry near Nelson and others from the Taranaki region.

We plan to divert the stream back into this first section of the new channel in January 2018. Fish will be kept out of the stream for some time while we continue working on the lower sections.

Te Puka Stream

The new permanent Te Puka Stream channel under construction.

We’re also working on a new permanent channel for the Horokiri Stream. The Horokiri is a wider and shallower waterway than Te Puka and has different requirements. Each stream has been specifically designed to most closely mimic the natural watercourse we are replacing.

A section of the new Horokiri Stream has been livened, with a blessing from Ngati Toa kaumatua. We re-used material reclaimed from the old stream and have had excellent feedback from Greater Wellington Regional Council, and the ecologists involved in the project on the results achieved.

Horokiri Stream

A livened section of Horokiri Stream. Textured concrete walls can be seen in the background for one of the bridges that will cross over the stream.

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Battle Hill Farm Forest Park

You can now see visible progress of the Battle Hill earthworks from the park’s Puketiro Loop track(external link).

Paekakariki Hill Road and Flightys Road

Bulk earthworks underway between our site compound at Paekakariki Hill Road and Flightys Road.

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South of State Highway 58

Bulk earthworks underway near Belmont Park

Bulk earthworks underway near Belmont Park.

From Lanes Flat, past Whitby and through the Belmont Regional Park, bulk earthworks continue to be the focus of the team. Construction has also started for a number of structures that will provide access under the motorway for users of Belmont Regional Park. Check out the Belmont Regional Park map for areas where you can safely view works underway.

Gas pipeline relocations through this area are complete and the switch over to the new lines will take place in the new year.

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Cannons Creek bridge construction

Cannons Creek Bridge launch area

A ‘launch area’ has been cleared at the site of the Cannons Creek Bridge, which will store materials for the girder installation set to take place in 2018.

Construction of the pier foundations for the Cannons Creek Bridge continues at pace with a number of concrete pours happening through January. The launch pad for the girder installation is now complete and construction of the specially fabricated launch mechanism will begin in the new year. We’ll have more on this impressive piece of engineering in our next project newsletter. In the meantime, check out the latest animation below showing how the bridge will be launched over the gully.

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State Highway 1

The structures that will form the Kenepuru Interchange and the tie-in to State Highway 1 at Linden are progressing well. Motorists will have noticed the large columns in place on either side of the motorway. People have asked why some columns are ‘fluted’ and some are not. The columns with flutes will remain visible once the bridges are complete, whereas earth fill will cover up the smooth columns.

Several retaining walls are under construction along the eastern (Greenacres) side of State Highway 1, south of the Collins Avenue bridge. We’re working closely with the local community and relevant authorities to design a series of artworks for these walls.

In the week between Christmas and New Year, we’ll be taking advantage of KiwiRail’s regular maintenance shut down on the main trunk railway line, to lift the girders in place for the bridge that crosses over this section of railway line. You’ll be able to check out the time-lapse of this installation on our website early next year.

A section of the Te Ara Tawa pathway that passes through this area is currently closed to the public for safety reasons. Please follow the signs for the alternative route along Kenepuru Drive. The path will re-open to the public in January 2018, once the girder installation is complete.

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Keeping you up to date

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We hope you enjoy reading these updates, and we’d love to hear from you. If you have any questions, comments or story suggestions, you can email them to info@tg.co.nz.

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